# What is the difference between a colloid and a solution?

A solution consists of a single phase whereby a solute is solvated by a solvent. For example, $K C {l}_{\text{(s)" + H_2O -> KCl_"(aq)}}$.
A colloid consists of more than 1 phase - for example, it could be solid in gas (smoke), two immiscible liquid phases (oil/water emulsion), or maybe gas in liquid (shaving foam). The key point is that there is not a single phase but two phases which exist as a stable suspension. Technically, a colloid should have a mean particle size between 1 and 1000 $n m$.